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Tempering CPM 154

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by elementfe, Sep 16, 2012.

  1. elementfe

    elementfe

    May 3, 2008
    Looking at the tempering table from Crucible,
    http://www.trugrit.com/CPM154HeatTreatSpecs.pdf
    results are pretty similar at tempering temps of 400-900 F, depending on quench.
    Can I imply that if I temper at 400, then overheat it while grinding, it won't affect hardness? I doubt I'll be going over 900 during grinding...
    After badly warping my last batch (I think I laid them on my anvil to cool some more while they were still hot enough to matter) I'm thinking a grind in the hardened state might be smart, in case of slight warpage.
    Thanks,
    Andy
     
  2. mete

    mete Gold Member Gold Member

    Jun 10, 2003
    Wrong way of thinking !
    If you have a warping problem take care of that first . 1200 F stress relieve before HT is a good idea.
    Don't assume that you'll only do 'a little damage' by heat during grinding. It's very easy to do a lot more damage and quicker than you think especially the very edge and tip !
     
  3. HardedgeKnives

    HardedgeKnives KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Feb 1, 2010
    Hello elementfe,
    If I understand right, you are having blade warpage during the hardening step of the heat treat and you would like to solve this by hardening and tempering first then grinding. I also have problems with warpage at this step but the really nice thing about this steel is that it takes a while to get hard after the quench which gives you a little time to straighten the blade. There are several quenching techniques (air fans, aluminum blocks, oil quench, etc.) and I use forced air fans. After the blade cools down to a couple of hundred degrees (about 10 min.) the steel is still quite soft (lots of austenite still in the process of transforming to martensite) and its easy to straightenbefore becoming fully hard.
    Kelley
     
  4. elementfe

    elementfe

    May 3, 2008
    Thank you Mete (I was hoping you'd see this) and Hardedge!

    I do that all the time with "carbon steels," straighten after quench, wasn't aware that it was an option with 154, thank you.

    Mete, I'll definitely do the stress relief next time around- this was a batch of six folder blades for a local show, and though they were all salvageable, they're definitely going in the Seconds case...sad but not too surprising, still crawling up the learning curve.
    I was careless during cooling, didn't stand them up on edge after the plate quench, so perhaps they warped while lying on a cold anvil...
     
  5. mete

    mete Gold Member Gold Member

    Jun 10, 2003
    That might be right. I was involved with a warping problem , perhaps on this forum, that was a real puzzle. We had to go through the entire process in great detail but in the end we found it was caused in cryo !! He had put the blade down on it's side and one side cooled faster and warped the blade !
     
  6. elementfe

    elementfe

    May 3, 2008
    Mete, what I wanted to ask you was, if the tempering temperature produces the same results from 4-900 Deg F, does it still ruin the blade if I temper at 400 and then raise the temp of part of the blade higher than that?
    Mostly just curious at this point, what's going on with the steel structually and chemically.
    Thanks!
     
  7. mete

    mete Gold Member Gold Member

    Jun 10, 2003
    Probably wouldn't hurt it but I'd like to then temper the whole blade to 900F.
    Problem is you don't know exactly how hot the blade got.
     
  8. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Dealing with warp is one good reason for having blades done in batches by a professional HT shop. I have Peters do mine now, and they straighten and Rc test each blade as part of the treatment. When I have forty blades done, it is saving me a lot of time....and I know they are straight. On thin blades I grind post HT, and just keep vigilant that the edges don't get overheated. Sharp belts are the trick in that department.
     
  9. elementfe

    elementfe

    May 3, 2008
    Bladsmth, I'm beginning to see the light on this one: having a batch of six blades go sideways is one thing if you're just practicing and a whole nother when getting inventory ready for a show...
     

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